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Transparent JFrame using JNA

In Make JFrame transparent I had shown a way to making frame’s transparent using AWTUtilities class. But using that class results in access restriction compile time error, resolution in Eclipse is also shown in that post. Now here is the version using java natives. I have used Java Native Access (JNA) library to call native functions to get the things done.

What is Java Native Access (JNA)?

JNA provides Java programs easy access to native shared libraries (DLLs on Windows) without writing anything but Java code—no JNI or native code is required.JNA allows you to call directly into native functions using natural Java method invocation.

The Code

import javax.swing.JFrame;
import javax.swing.JSlider;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

import com.sun.jna.platform.WindowUtils;

public class TransparentFrame extends JFrame {
   public TransparentFrame() {
      setTitle("Transparent Frame");
      setSize(400,400);
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      JSlider slider = new JSlider(JSlider.HORIZONTAL, 30, 100, 100);

      slider.addChangeListener(new ChangeListener() {
         @Override
         public void stateChanged(ChangeEvent e) {
            JSlider slider = (JSlider) e.getSource();
            if(!slider.getValueIsAdjusting()){
               WindowUtils.setWindowAlpha(TransparentFrame.this, slider.getValue()/100f);
            }
         }
      });
      add(slider);
      setVisible(true);
   }
   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
	 @Override
	 public void run() {
	    new TransparentFrame();
	 }
      });
   }
}

Here WindowUtils class is provided in JNA jar (platform.jar). The method setWindowAlpha of WindowUtils class is used to make a window transparent. First argument of this method is your frame/window and second argument is alpha value. This class also has a method called setWindowTransparent, which can also be used to make window transparent .

Dependencies

You will need following 2 jars to run this program: (Both jar files are available to download on GitHub for JNA.)

  • jna.jar
  • platform.jar

To run above code on Windows, you will need to set “sun.java2d.noddraw” system property before calling the WindowUtils function.

System.setProperty("sun.java2d.noddraw", "true");

Output

Additional Notes

I have tested this code on following machines:

  • Windows XP service pack 3 (32 bit)
  • Windows 7 (32 bit)
  • Cent OS 5 (32 bit)

If you test it on other machines or have code for other machines using JNA for the same functionality then feel free to share it as comment to this post.

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Make JFrame transparent

How to create a slider for JFrame transparency and make JFrame transparent accordingly?

First create a frame that has a slider in it which will be used to set transparency amount.

import javax.swing.JFrame;
import javax.swing.JSlider;

public class TransparentFrame extends JFrame {
     public TransparentFrame() {
         setTitle("Transparent Frame");
         setSize(400,400);
         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         JSlider slider = new JSlider(JSlider.HORIZONTAL);
         add(slider);
         setVisible(true);
     }
     public static void main(String[] args) {
         new TransparentFrame();
     }
}

Output of this will be:

Now add a change listener to slider so we can monitor it.


slider.addChangeListener(new ChangeListener() {
       @Override
       public void stateChanged(ChangeEvent e) {
       }
});

Now we will write our transparency logic in this method but before we do that first let’s see how to make a JFrame transparent.

To make a JFrame transparent java has a built in utility class that is AWTUtilities. By using methods provided in this class we can make our JFrame transparent. Following is the code for that:

       AWTUtilities.setWindowOpacity(window, floatOpacity);

Arguments:

                  Window – Your frame/window object.

                  floatOpactity – between 0 to 1.  1 for no opacity and 0 for fully transparent.

So now we know that we have to add this logic to slider change event and give sliders value as floatOpacity value. So for that change stateChanged() method with following:

@Override
public void stateChanged(ChangeEvent e) {
      JSlider slider = (JSlider) e.getSource();
      if(!slider.getValueIsAdjusting()){
            AWTUtilities.setWindowOpacity(TransparentFrame.this, slider.getValue());
      }
}

Think it’s done. No we still have to make sure that opacity value doesn’t go beyond its limit that is 0.0f to 1.0f. So for that we have to limit our slider to these values. As slider don’t supports point values we will take values in multiple of 10 and then divide them by 100 to get desired value. For this we will change JSlider declaration and stateChanged like follow:


JSlider slider = new JSlider(JSlider.HORIZONTAL, 10, 100, 100);

Change following line in stateChanged method:


AWTUtilities.setWindowOpacity(TransparentFrame.this, slider.getValue()/100f);

So now when we run this program we see a frame with a slider in it which is set to end. And when we change slider the frame accordingly change its transparency.

Output:-

Note:-

To use AWTUtilities class in eclipse you need to change preference setting or you may have error for accessing restricted classes. To change settings do as follows:

  1. Right click on your project. Select properties.
  2. Select Java compiler and expand it.
  3. Select Errors/Warnings.
  4. Enable project specific settings.
  5. In Deprecated and Restricted API you will find Forbidden References (access rules.) Change it to Warning or Ignore.
Reference:

Also take a look take: Transparent JFrame using JNA

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